1. Field of the Invention
The present invention relates to a novel protease which hydrolytically cleaves a peptide bond between two adjacent basic amino acids present in a peptide chain, and a process for production of the protease.
2. Description of the Related Art
Usually two basic amino acids are adjacent in a prohormone, i.e., a precursor of peptide hormone, such as adrenocorticotrophic hormone, melanocyte-stimulating hormone, .beta.-lipotropin, .beta.-endorphin, .alpha.-neoendorphin, insulin, or the like. In such cases, the prohormone is activated to its active hormone by cleavage of a peptide chain of the prohormone at an N-side, C-side, or middle of the adjacent two basic amino acids, and the activation is carried out by a corresponding enzyme protease.
Recent progress in the field of genetic engineering has brought to light the possibility of microbial production of many kinds of higher animal hormones, wherein mRNA's coding for a prohormone are obtained from an animal, cDNAs are prepared from the mRNA, the cDNAs are screened, and the selected cDNA is incorporated into a appropriate vector which is then transformed into a host. In such a case, often an inactive prohormone rather than active hormone is expressed. Therefore, to obtain an active hormone, the prohormone must be artificially processed by a processing enzyme. In such a situation, the above-mentioned proteases are of practical interest.
Kurjan J. et. al., Cell, 30, 933-943, (1982); and Julius D., et al., Cell, 32, 839-852 (1983) describe a membrane-bound dipeptidyl aminopeptidases which processes a precursor polypeptide to form a yeast .alpha.-factor. This enzyme cleaves a carboxyl side of repeating-X-Ala-sequences, however, this action is different from that of the protease of the present invention.
Proteases from an animal that cleave a peptide bond between two adjacent basic amino acids in a peptide chain are described by Fletcher et. al., J. Cell Biol., 90, 312-322 (1981); Loh Y. P. et. al., Proc. Natl. Acad. Sci. U.S.A., 79, 108-112 (1982); Mizuno et. al., Biochem. Biophys. Res. Commun., 108, 1235-1242 (1982); Lindberg I. et. al., Biochem. Biophys. Res. Commun., 106, 186-193 (1982); Evangelista R. et. al., Biochem. Biophys. Res. Commun., 106, 895-902 (1982); and Fricker L.D. et. al., Proc. Natl. Acad. Sci. U.S.A., 79, 3886-3890 (1982). All of these enzymes are different from the protease of the present invention in detailed properties, including specificity to substrates and response to various inhibitors. Moreover, these known enzymes are difficult to produce industrially because they are derived from animals.